OH !! and Phil Sc, sorry for the thread HIjack, but your post was very timely for me as I am doing the same thing you are at this time, My appoligies for the interruption..............;-)
Rotto
no problem it turned out to be a informative post
as for my research a friend of mine is an electrical engineer and this is his suggestion
Phil,
The final answer is in.
Connect as follows:
Battery negative terminal via hefty cable to the single point ground on the firewall.
From that point, to the engine crankcase near the starter motor with welding cable.
Connect a 10AWG wire between a nearby lug on the frame to the single point ground.
Radios etc should also connect to the single point ground (the B&C forest of tabs is good for this).
The single point ground should be bolted right through the firewall (brass), so there is a ground point on both sides.
The reasoning is this. Steel is a poorer conductor than copper, so you are adding additional resistance in the starter current path. This works out to one less connection in the starter current path as well, also reducing resistance. Although this resistance sounds small, it has a significant effect at starter currents.
Also, as I mentioned before, the steel frame will become magnetized.
2AWG versus 4AWG for the all the heavy cables (plus and minus) will cost you 2.2 pounds and reduce the voltage drop on the cable to the starter by only 4%.
The quality of these connections is more important than the resistance of the wire. Make them well.
Cheers,
Jeff